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Inconsistent Groups

 
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  #1  
Old 06-21-2011, 10:25 PM
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Join Date: Jun 2011
Location: WY
Posts: 164
Inconsistent Groups

I've lurked around here long enough combing these threads that are full of excellent information. My problem is this: I've been trying to work up loads in my 264 WM and cannot seem to get consistent results. I started with 140 gr vlds and couldn't get any powder to group well - everything was 1.5 - 2.0 moa. Tried 130 grain vlds and got the same results. Changed from CCI to WLRM primers and all three powders I was working with produced sub moa groups! Chose to work up with WIN 780 Supreme based on book velocity. Worked up to 67.0 grains with no pressure signs. 66.0 produced a .34" 3 shot 100 yd group. At this time, I ran out of new brass - I neck sized a few (with a neck-sizing die) and chambered to insure neck sized loads would function properly. Back out to the bench with the once fired neck sized loads - really sticky bolt and no group (1.5 - 2.0 moa). Went back through the lot of brass and full length sized all (these had all been full length sized, fired once, and neck sized) brass. Various powders (win 780 supreme, 7828ssc, H1000) all will shot terribly inconsistent .5" one time, 1.5" a half hour later. Also, now I'm getting pressure signs (sticky bolt, cratered primers) with 66.0 gr of 780 supreme (with full length sized brass)!

Why am I getting pressure signs with a load that was already worked up in the same rifle - same lot of powder, primers, bullets, and twice fired brass? Did sizing the brass twice (neck sized, then full length) without firing in between mis-shape the brass? All brass measurements are consistent with book dimensions. Tonight I re-checked all action bolts, base / ring screws, etc.

What say you?
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  #2  
Old 06-22-2011, 07:27 AM
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Re: Inconsistent Groups

The temperature of the cartridge before it is fired is important. If it sit out in the sun or is allowed to sit in a already hot chamber it will affect the pressure.

I would suggest you try RL22 and Fed 215 primers. If that will not give you good groups then consider that the problem may be somewhere else. Accuracy can be affected by parallax, bedding, barrel contact, poor bench skills, flinching, etc.

If you can normally shoot half inch groups at 100 yards then you can pretty much rule out some problems but if not then you simply should realize that reloading technique does not compensate for poor shooting skills. This is much like the ability to shoot small groups does not compensate for not being able to find an animal to shoot at.

Seating depth on VLDs is often a critical issue.
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  #3  
Old 06-22-2011, 08:13 AM
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Location: Rapid City, South dakota
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Re: Inconsistent Groups

Almost looks like your throwing too many variables into the works. When I start a new gun I will break in the barrel by finding a load a grain or so less than max and don't care what the accuracy is with it as I know this will change as I use new brass and the cheapest bullets I can find and besides breaking in the barrel with this load I am also fire forming my brass. Once the brass is all fire formed and the barrel broke in, (shoot clean, shoot clean etc. for 30 rounds and then shoot 5 clean, shoot 5 clean for another 20 rounds) I then end up with 50 cases that I neck size and trim to length and then begin my load work up. I also anneal those cases before sizing so I get consistent neck tension. I seldom use any powder besides one of the Hodgdon Extreme powders especially at this time of year. Outside temps can cause too many variables for me to deal with. When you bounce around from New case to neck size case to full length size case it introduces too many variables. Just pick one and work from there.
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  #4  
Old 06-22-2011, 12:30 PM
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Re: Inconsistent Groups

Seems that you have shot a lot of loads. Have you cleaned the bore with copper solvent? It could also be a buildup of copper fauling.
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  #5  
Old 06-22-2011, 09:01 PM
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Posts: 164
Re: Inconsistent Groups

I broke in the barrel with 1 shot / clean for the first 10 rounds. Then 3-shot groups (beginning load development) - clean. Once I'd shot 30 rounds, I shot 5 shot groups (continuing load development) - clean. From about 50 til now (just over 200) I clean after ever 10 - 15 rounds (carbon and copper everytime). I've tried to concentrate on neck sized brass / win 780 supreme loads adjusting seating depth and powder amount and just don't have any consistency. A few times, I've gone back to some other powders that shot well with new brass (7828ssc & H1000). Both of these powders shot sub-moa with new brass and now will not group.

The only other difference since I started is the weather has warmed 20 - 25 degrees. Maybe 780 supreme is temp sensitive?

I don't think it's shooting form, bench practices, etc. Just to make sure, I shot 3 other rifles from the same set up. All were around .5 moa at 100 yards.

I do run one oil patch down the bore (followed by a dry) after cleaning carbon and copper. I've heard some folks say it takes a dozen rounds to burn out oil - others swear by running an oil patch through???? Doesn't seem to make a difference in my other rifles.

The rifle is a stainless cdl in 264 win mag. I put on a Bell and Carlson Medalist stock (with aluminum bedding block), and a VX3 6.5-20x50 LRT with talley one piece rings. Last night I checked all action screws and scope mount screws again.

Maybe I just need to work up different loads now that the barrel is broke in instead of trying to force another 0.34 group with 780? I've got a bedding kit ordered. I guess the next order of business is bolt trueing?

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  #6  
Old 06-23-2011, 08:26 AM
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Join Date: Jun 2010
Posts: 372
Re: Inconsistent Groups

I use a lot of 130 VLDs in my 6.5-284 and I use a carbon remover every 30-40 shots. I remove copper after about 100. This seems to work well for me. VLDs are sensitive to seating depth I am sure you have noticed. Go back over your reloading process and find your inconsistency. make sure you do exactly the same thing every time. Do you measure the OAL of every round? The first good thing I noticed you did was switch to winchester primers. some swear by CCI but the only consistent CCI primer I have found were magnums and that was in non magnum rounds. in summer back down to a standard primer. The powder is easier to ignite (to my understanding and experience) in higher temps of the summer. are the outside conditions the same from one day to the next when you are testing your loads? aside from temp check the barametric pressure at the nearest airport. Type in your zip code on weather.com and it will give you the pressure reading at the nearest airport with an ASOS system, then verify the difference in your altitude and that of the airport, from that look online to find how to calculate your pressure. if you are within 100 feet of altitude then there is no need to check it, it will get you close enough that it should not effect your shooting. bullets fly different when the pressure is different, and at some velocity/chamber pressure you will find a spot with the least deviation. Are you checking each shot on a Chronograph? These are a few subtle changes I have found to effect my groups that not everyone looks at. Again though, I would bet it is an inconsistency in your process somewhere. We all do it and have to check and recheck on a regular basis. Hope some of this helps. Some will say that I am sending you on a witch hunt with the pressures and what not, but I almost always find a discrepency when this is happening to me and I know my process is sound. Last thing, how much case stretching are you getting with each shot fired, and did you trim your cases. Failing to trim when needed is a sure fire group killer and can add pressure, the type of differences you are seeing. Been there and done that and the only way to find the issue is to go looking for it. a number of things can cause it.
Last but not least is your shooting form and rest. I have a 22-250 Encore rifle that absolutely will not shoot the same with any load on any given day as the day before IF I rest the fore end in a vice type rest. However if I just rest it on sand bags I will consistently get the same results. What brand of brass are you using? if it is remington, I suggest throw it away and get winchester, nosler, or just about anything but remington. RP brass tends to be soft and I have found it to be at near max length even before firing the first shot. In my 300 win mag it tends to stretch and need trimming after the first shot is fired. In that rifle it absolutely will not chamber until it is trimmed. Hope you get where you need to be. I am sure I repeated someone at some point here but only in the interest of being thorough.

Try some RL25 if 7828 isn't working for you. Accuracy trumps velocity in almost every instance. I am sure you know that, but it took me years to figure it out for myself.

Last edited by cfvickers; 06-23-2011 at 08:30 AM.
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  #7  
Old 06-23-2011, 09:13 PM
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Join Date: Aug 2003
Location: NC, oceanfront
Posts: 3,270
Re: Inconsistent Groups

I don't understand all your abstracts in sizing.
For load development, you should decide what size your brass will always be and put it there beforehand.

New brass could be anything.
NS'd only brass is different than new, or FL sized brass.
Neck sizing before/after FL sizing is one sizing too many.
You can't base pressure on case extraction until you know/standardize what sizes your cases are before firing.
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